net/ipv4/netfilter/ipt_REDIRECT.c

   1 /* Redirect.  Simple mapping which alters dst to a local IP address. */
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/ip.h>
  12 #include <linux/timer.h>
  13 #include <linux/module.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netdevice.h>
  16 #include <linux/if.h>
  17 #include <linux/inetdevice.h>
  18 #include <net/protocol.h>
  19 #include <net/checksum.h>
  20 #include <linux/netfilter_ipv4.h>
  21 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  22
  23 MODULE_LICENSE("GPL");
  24 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  25 MODULE_DESCRIPTION("iptables REDIRECT target module");
  26
  27 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(format, args...)
  31 #endif
  32
  33 /* FIXME: Take multiple ranges --RR */
  34 static int
  35 redirect_check(const char *tablename,
  36                const struct ipt_entry *e,
  37                void *targinfo,
  38                unsigned int targinfosize,
  39                unsigned int hook_mask)
  40 {
  41         const struct ip_nat_multi_range_compat *mr = targinfo;
  42
  43         if (strcmp(tablename, "nat") != 0) {
  44                 DEBUGP("redirect_check: bad table `%s'.\n", table);
  45                 return 0;
  46         }
  47         if (targinfosize != IPT_ALIGN(sizeof(*mr))) {
  48                 DEBUGP("redirect_check: size %u.\n", targinfosize);
  49                 return 0;
  50         }
  51         if (hook_mask & ~((1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT))) {
  52                 DEBUGP("redirect_check: bad hooks %x.\n", hook_mask);
  53                 return 0;
  54         }
  55         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  56                 DEBUGP("redirect_check: bad MAP_IPS.\n");
  57                 return 0;
  58         }
  59         if (mr->rangesize != 1) {
  60                 DEBUGP("redirect_check: bad rangesize %u.\n", mr->rangesize);
  61                 return 0;
  62         }
  63         return 1;
  64 }
  65
  66 static unsigned int
  67 redirect_target(struct sk_buff **pskb,
  68                 const struct net_device *in,
  69                 const struct net_device *out,
  70                 unsigned int hooknum,
  71                 const void *targinfo,
  72                 void *userinfo)
  73 {
  74         struct ip_conntrack *ct;
  75         enum ip_conntrack_info ctinfo;
  76         u_int32_t newdst;
  77         const struct ip_nat_multi_range_compat *mr = targinfo;
  78         struct ip_nat_range newrange;
  79
  80         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
  81                      || hooknum == NF_IP_LOCAL_OUT);
  82
  83         ct = ip_conntrack_get(*pskb, &ctinfo);
  84         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  85
  86         /* Local packets: make them go to loopback */
  87         if (hooknum == NF_IP_LOCAL_OUT)
  88                 newdst = htonl(0x7F000001);
  89         else {
  90                 struct in_device *indev;
  91
  92                 /* Device might not have an associated in_device. */
  93                 indev = (struct in_device *)(*pskb)->dev->ip_ptr;
  94                 if (indev == NULL || indev->ifa_list == NULL)
  95                         return NF_DROP;
  96
  97                 /* Grab first address on interface. */
  98                 newdst = indev->ifa_list->ifa_local;
  99         }
 100
 101         /* Transfer from original range. */
 102         newrange = ((struct ip_nat_range)
 103                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
 104                   newdst, newdst,
 105                   mr->range[0].min, mr->range[0].max });
 106
 107         /* Hand modified range to generic setup. */
 108         return ip_nat_setup_info(ct, &newrange, hooknum);
 109 }
 110
 111 static struct ipt_target redirect_reg = {
 112         .name           = "REDIRECT",
 113         .target         = redirect_target,
 114         .checkentry     = redirect_check,
 115         .me             = THIS_MODULE,
 116 };
 117
 118 static int __init init(void)
 119 {
 120         return ipt_register_target(&redirect_reg);
 121 }
 122
 123 static void __exit fini(void)
 124 {
 125         ipt_unregister_target(&redirect_reg);
 126 }
 127
 128 module_init(init);
 129 module_exit(fini);